Diathermy apparatus



Jan. 18, 1938. A. H. MccLELLAND 2,105,749

DIATHERMY APPARATUS Filed May 5, 1936 2 Sheets-Sheet 1 l I I' EF Z5 l" CHoKE l /4 v q' 1 l 5b l |I 5a 5 n 3 5b ,r

PLATE COPETTUK GRID' CONNECTOR CONETES T0 Tl/NlN To 'run/NG CaNDsNaE. C ONDENsEz INVEN TOR.

r/zur McClelland BVM'. 2.

Jan. 18, 1938. 'A. H. MccLELLAND 2,105,749

DIATHERMY APPARATUS Filed May 6, 1936 2 Sheets-Sheet 2 5b 5b P," .J. [MMV #A y 24mm INSULATION /yf`\\ I Treatment Electr Carnac Lon INSULATION gnu-croc INV EN TOR.

,y UNITED STATES PATENT OFFICE DIATHERMY APPARATUS Arthur H. McClelland, Los Angeles, Calif., assignor to Edgar J. Rose, Los Anales, Calif.

Application May 6, 1936, Serial No. 78,180

3 Claims.

This invention relates to vacuum-tube diaf thermy circuits and pertains particularly to a band-switching circuit arrangement for varying the output frequency of a high frequency diathermy generator.

One of the important objects of the invention is to provide a band-switching circuit arrangement having relatively low losses at the highest frequency to which the circuit may be established.

A further object of the invention is to provide a band-switching circuit arrangement in which a portion of the inductance of an oscillating circuit may be shorted out without producing voltage intensications in such inductance in a relation which will affect the efficiency thereof at the higher frequencies.

A further object of the invention is to provide an advantageous relation between the inductances in a high frequency vacuum tube generator.

A further object of the invent-ion is to provide an advantageous band-switching arrangement for varying the output frequency of a high-frequency vacuum-tube generator.

The vacuum-tube circuit of the present invention may comprise a self-excited balanced-circuit oscillator such as a push-pull circuit in which the plates of two tubes are connected to opposite ends of a tank inductance which is center-tapped to the high tension side of a power transformer, and means for shorting a predetermined number of turns at the center portion of said inductance to vary the period of the oscillatory circuit, and in which the oscillating circuit is coupled to an output circuit at a portion of the aforesaid tank inductance which has a minimum inductive coupling to the balance of said inductance. In its preferred embodiment the portion of the tank inductance which is coupled to the output circuit is caused to constitute the entire eifective inductance for the oscillating circuit at the highest frequency to which the period of the high frequency generator may be adjusted.

Other objects of' the invention will be brought out in the following description of a preferred embodiment of the invention, or will beapparent therefrom. The accompanying drawings illustrate such a preferred embodiment and referring thereto:

Fig. l is a plan view of the arrangement of inductances and coupling capacities for the highfrequency generator portion of the circuit;

Fig. 2 is a vertical section thereof taken on line 2 2 in Fig. 1;

Fig. 3 is a front elevation thereof;

Fig. 4 is an end elevation thereof;

(Cl. P11-119) Fig. 5 is .a schematic showing of the circuit of the present invention; and

Fig. 6 is a sectional detail taken on line 6 6 in Fig. 3

Referring to the drawings, and Fig. 5 in par- 5 ticular, two three-element vacuum tubes are indicated at I, provided with plates 2, grids 3, and filaments or cathodes 4. The plates 2 of the respective tubes are connected to opposite ends of a tank inductance each half of which may com- 10 prise, for example, a one and one-half turn minor coil section 5a and an eight turn major coil section 5b, said sections 5a and 5b being disposed with their axes substantially at right angles to one another to provide a minimum inductivecoul5 pling therebetween, i. e., disposed in non-mutual inductive relation. 'Ihe grid 3 of each tube is capacity coupled to the plate of the other tube, as through coupling condensers 6, and the grid supply for the tubes is obtained through radiofrequency chokes 1 and a center-tapped grid resistor 8 connected to the center of the filament transformer 9 through a lead I0 and automatic bias resistor II. The plate circuit may be completed from the resistor II through a plate milliammeter I2 to the one high voltage terminal of a power transformer I3, the other high Voltage terminal of said transformer being connected to the center of the tank inductance through a suitable radio-frequency choke I4. The tank coilportions 5a are shown coupled in a fixed relation to the output circuit pick-up coils I5 which are preferably of the same relative dimensions as the coils 5a. and whose magnetic axes are in approximate coincidence with those of the coils 5a. The 3 output circuit may also include a variable condenser !6 connected to the inner ends of the coils I5 as shown in Figs. 2 and 5, and a pair of suitably insulated spaced treatment electrodes II connected to the outer ends of said coils as shown 'in Figs. 3 and 5, which spaced electrodes may define a diathermy treatment zone indicated by the dotted circle I8. Control of thc energy dissipation in the treatment circuit may be obtained by variation of the condenser I6, as will be appreciated by one skilled in the art.

The frequency of the generating circuit is established at any one of a plurality of desired]l frequencies by snorting-out a portion of the tank coil-portions 5b, and at the highest frequency to 50 which the circuit may be adjusted the tank coilportions 5a may constitute the entire tank inductance of the circuit. 'I'he particular circuit shown in the drawings is adapted for adjustment to 6,

9, 12, and 16 meters, the coils 5a comprising one 55 and one-half turns each and the coils 5b comprising eight turns each. At 16 meters the coils 5a and 5b are connected in series at the highpotential ends of the coils 5b and the full inductance thereof employed. At 12 meters I short out approximately three turns at the low-potential end of each of the coil portions 5b, as at 5c, and at 9 meters I short out two additional turns in each coil as at 5d. The shorting is conveniently effected by providing a plurality of jacks mounted on stand-off insulators and electrically connected to the respective portions of the coil portions 5b and defining contact members adapted to receive a plug-in connector or shorting bar 2| as shown in Fig. 6 and by a dotted line in Fig. 5.

Where the minimum tank inductance is employed, the coil portions 5a may constitute the entire effective inductance for the oscillating circuit, as above set forth, and in view of the fact that the respective portions 5a are disposed with their magnetic axes substantially at right angles to the axes of the coil portions 5b, the coupling between the respective portions 5a and 5b is at a minimum, whereby losses in the shorted portions 5b are kept at a minimum, contributing materially to the output efficiency oi the circuit at the G-meter band.

Referring more particularly to Figs. yl to 4, the several inductances are shown as mounted on a sub-panel 22 through the agency of stand-off insulators 23, certain of which insulators are provided with jacks as above described. Referring particularly to Fig. 3, insulated jacks are shown at 24, 25, 26, and 2l', the jacks 24 being connected to the electrical center or low potential ends of the coils 5b, from which connection is provided to the transformer |3 through the radio-frequency choke I4 as above described. The jacks 25 connect respectively to points on the coils 5b two and three-fourths turns removed from the connection of the jacks 24. The jacks 26 connect to said coils 5b at a point five turns in from the connection of the jacks 24 and the jacks 2l connect to said coils 5b at their plate sides. The connector 2| may comprise a U-shaped connector 2 la having its middle portion embedded in a rubber or other insulating handle or cover 2| b, the two projecting portions of the connector being adapted to extend through the main panel and enter Within the opposing jack combinations 24-24, 25-25, and the like in the sub-panel 22. Thus the connecting means 2| is shown short circuiting the jacks 26 in Figs. 3 and 4 and is indicated in a corresponding position by the dotted line 2| in Fig. 5.

The coupling condensers 6 are preferably mounted on opposite sides of an insulating support 3| carried by suitable posts 32 secured to the panel 22, and are disposed rearwardly of the coil portions 5a and 5b and removed from the fields thereof. The plate leads 33 are provided with suitable plate connectors and are attached at one end to the condensers 6 as at 34, which connection is carried over to the plate side of the coils 5a as at 35. The other side of each condenser is connected as at 36 through a suitable lead 3l to the grid of the opposite tube as indicated particularly in Fig. 1.

The main panel, indicated at 38 in Figs. 4 and 6, is provided with eight openings 38 in line with the respective openings in the jacks 24 through 21 and may be suitably engraved with markings denoting the respective frequency bands. The main panel preferably carries a control knob for the condenser I6, as well as the necessary indicating instruments such as the milliammeter 2, switches and the like.

I claim:

1. In a vacuum tube diathermy apparatus, a band-switching generating and output circuit assembly which comprises: tank inductance means including a plurality of coil sections provided with means for short circuiting any desired portion of such sections to vary the effective inductance of said inductance means, said inductance means being divided into two electrically balanced halves, each half including a major coil section and a minor coil section in non-inductive relation to one another, said major coil sections of said two halves being disposed in spaced relation along a common magnetic axis; and a pickup circuit including a pickup coil disposed in inductive relation to each of said minor coil sections.

2. In a vacuum tube diathermy apparatus, a generating and output circuit assembly which comprises: a pair of identical and symmetrically arranged tank induotances each having a portion arranged along a magnetic axis common to said pair and electrically connected to the other at its outer end and each having a coupling coil portion in non-inductive relation to the portion thereof arranged along said axis; a pickup coil located adjacent each coupling coil, and in inductive relation thereto; and means for reducing the eii'ective inductance of said tank inductances by like amounts comprising means for establishing electrical connection between a point on one of said inductances and an equivalent point on the other of said inductances whereby the extremities of said inductances between said points and the outer ends are short circuited and rendered ineffective.

3. In a balanced-circuit vacuum tube diathermy apparatus, a band-switching tank inductance assembly which comprises: a sub-panel; two coil members mounted on said sub-panel along a common magnetic axis and spaced from one another along said axis and electrically connected together at their outer ends; a coupling coil electrically connected to the inner end of each of said coil members, said coupling coils being mounted on said sub-panel with their magnetic axes substantially parallel to one another, substantially normal to the direction of said common axis, and spaced outwardly from said inner ends of said coil members in the direction of said common axis; a pickup coil mounted on said subpanel in inductive relation to and alongside each of said coupling coils, at the side thereof outwardly removed from the respective coil members; a plurality of Contact members mounted on said sub-panel and arranged in a plurality of equally spaced pairs; electrical connector means connecting the respective contacts of each of said pairs to spaced and inductively equivalent points on each of said coil members, to provide connection of the respective contact members of each of said pairs to inductively equivalent portions of said two coils; and a connector member adapted to contact the two contact members of any one of said pairs to short circuit across said inductively equivalent portions of said firstmentioned coil members.

ARTHUR H. MCCLELLAND. 

